Quelques precisions sur les effets catalytiques des micelles cationiques hydroxylees

The alkaline hydrolysis of p-nitrophenyl acetate and of CH₃CO₂(CH₂)₂N⁺(CH₃)₂C₁₆H₃₃, Br^? was studied in the presence of micelles C₁₆H₃₃N⁺(CH₃)₂CH₂CH₂OH, Br^? and CTAB, C₁₆H₃₃N⁺(CH₃)₃,Br^?. A pathway involving an intermediate is suggested for the hydrolysis of the ester. Hydrolysis rate of the intermediate in the presence of micelles is the same as hydrolysis rate for the ester in the absence of micelles. Consequently, hydrolysis of p-nitrophenyl acetate is not catalysed by one type of micelle, while it is enhanced by another type of micelle.     

Gas-phase ion equilibria studies of protons and chloride ions in propanol and acetone

The gas-phase clustering reactions of proton in propanol and acetone, and chloride ions in acetone were investigated. The −ΔH_n−1,n values obtained for clustering reactions (n−1,n) were as follows: H⁺ (C₃H₇OH)_n−1 + C₃H₇OH ⇄ H⁺ (C₃H₇OH)_n, (2, 3) 18.9 kcal mol⁻¹, (3, 4) 14.2 kcal mol⁻¹, (4, 5) 11.7 kcal mol⁻¹; H⁺ (CH₃COCH₃)₂ + CH₃COCH₃ ⇄ H⁺ (CH₃COCH₃)₃, 14.2 kcal mol⁻¹; and Cl⁻ + CH₃COCH₃ ⇄ Cl⁻ (CH₃COCH₃), 12.4 kcal mol.⁻¹. For clustering reactions, Cl⁻ (CH₃COCH_3n−1 + CH₃COCH₃ ⇄ Cl⁻ (CH₃COCH₃)_n where n ≥ 2, the equilibria could not be established; probably due to the isomerization of ligand acetone molecules from the keto to enol form.     

Synthesis of pyridine N-imine complexes of methylcobaloxime and reactions of bis(dimethylglyoximato)methyl(Pyridine N-imine)cobalt with acid anyhydrides and acetylenedicarboxylic acid dimethyl ester

Pyridine N-imine complexes of methylcobaloxime, CH₃Co(Hdmg)₂(R¹— C₅H_nN⁺N^?H) (n = 4; R¹ = H, 2-CH₃, 3-CH₃, 4-CH₃: n = 3; R¹ = 2,6-CH₃), have been synthesized by the reaction of CH₃Co(Hdmg)₂S(CH₃)₂ with a pyridine N-imine which is generated from a pyridine, hydroxylamine-O-sulfonic acid and K₂CO₃. The reactions of CH₃Co(Hdmg)₂(C₅H₅N⁺N^?H) with acid anhydrides form new methylcobaloxime complexes with N-substituted pyridine N-imines, CH₃Co(Hdmg)₂(C₅H₅N⁺N^?R²) R² = COPh, COMe, COEt). With maleic anhydride, (pyridine N-acryloylimine)carboxylic acid is formed. With acetylenedicarboxylic acid dimethyl ester, 1,3-dipolar cycloaddition of the ligand gives pyrazolo[1,5-a]pyridine-2,3-dicarboxylic acid dimethyl ester.     

Mixing Behavior of Conventional and Gemini Cationic Surfactants

Micellization behavior of cationic monomeric surfactants, hexadecyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC), tetradecyltrimethylammonium bromide (TTAB), and dimeric (gemini) cationic surfactant pentamethylene‐1, 5‐bis(hexadecyldimethylammonium bromide) with formula C₁₆H₃₃(CH₃)₂N⁺(CH₂)₅N⁺(CH₃)₂C₁₆H₃₃ · 2Br^?, abbreviated as 16‐5‐16, in mixed states (binary) have been studied by conductivity. The micellar compositions, activities of the components, and their mutual interactions have been estimated from Rubingh's theory. The mixtures show nonideal behavior with favorable interactions.     

Elucidating the structures of isomeric silylenium ions (SiC3H 9 + , SiC4H 11 + , SiC5H 13 + ) by using specific ion/molecule reactions

Specific ion/molecule reactions are demonstrated that distinguish the structures of the following isomeric organosilylenium ions: Si(CH₃) ₃ ⁺ and SiH(CH₃)(C₂H₅)⁺; Si(CH₃)₂(C₂H₅)⁺ and SiH(C₂H₅) ₂ ⁺ ; and Si(CH₃)₂(i?C₃H₇)⁺, Si(CH₃)₂(n?C₃H₇)⁺, Si(CH₃)(C₂H₅) ₂ ⁺ , and Si(CH₃)₃(π?C₂H₄)⁺. Both methanol and isotopically labeled ethene yield structure-specific reactions with these ions. Methanol reacts with alkylsilylenium ions by competitive elimination of a corresponding alkane or dehydrogenation and yields a methoxysilylenium ion. Isotopically labeled ethene reacts specifically with alkylsilylenium ions containing a two-carbon or larger alkyl substituent by displacement of the corresponding olefin and yields an ethylsilylenium ion. Methanol reactions were found to be efficient for all systems, whereas isotopically labeled ethene reaction efficiencies were quite variable, with dialkylsilylenium ions reacting rapidly and trialkylsilylenium ions reacting much more slowly. Mechanisms for these reactions and differences in the kinetics are discussed.     

Micellization and Thermodynamic Parameters of Butanediyl-1,4-bis(tetradecyldimethylammonium Bromide) Gemini Surfactant at Different Temperatures: Effect of the Addition of 2-Methoxyethanol

The effect of the addition of 2-methoxyethanol on the critical micelle concentration (cmc) and on the degree of counterion dissociation (??) of butanediyl-1,4-bis(tetradecyldimethylammonium bromide) gemini surfactant, [C₁₄H₂₉N⁺(CH₃)₂?C(CH₂)₄?CN⁺(CH₃)₂C₁₄H₂₉,2Br^?] (referred as 14?C4?C14,2Br^?), has been studied by varying the compositions of the 2-methoxyethanol + water mixed solvent media (0 to 50?%). To determine various thermodynamic parameters of micellization, on the basis of the mass?Caction model for micelle formation, the experiments were performed at selected compositions of the mixed solvent at four temperatures ranging between 25?°C and 50?°C. Furthermore, the air/bulk surface tensions of the pure and mixed media were determined, and a successful attempt was made to correlate the cohesive energy density described through the Gordon parameter with the values of Gibbs energy of micellization.     

Synthesis of a vinylcarbynetetrairon complex. Crystal and molecular structure of [(C5H5)2(CO)2Fe2(μ-CO)]2- (μ-C5H3)+BF4−

The diiron vinyl ether carbyne complex [(C₅H₅)(CO)Fe]₂(μ-CO)- (μ-CCHCHOCH₂CH₃)⁺ BF₄⁻ (1) reacted with the diiron ethenylidene complex [(C₅H₅)(CO)Fe]₂(μ-CO)(μ-CCH₂) (2) to yield the tetrairon complex [(C₅H₅)₂(CO)₂Fe₂(μ-CO)]₂(μ-C₅H₃⁺BF₄⁻ (3) which was characterized by spectroscopy and by single crystal X-ray diffraction.     

Fabrication and characterizations of mesoporous TiO2 and SiO2/TiO2 composite with high photocatalytic activity using a new Gemini surfactant

In this paper, mesoporous rod-like SiO₂/TiO₂ (m-SiO₂/TiO₂) and mesoporous sphere-like TiO₂ (m-TiO₂) have been prepared by using a new type Gemini surfactant containing carbonyl groups (GS-A, [(C _n H_{2n + 1})(CH₃)₂N⁺(CH₂)₂-O₂C-(CH₂)₄-CO₂-(CH₂)₂N⁺(CH₃)₂(C _n H_{2n + 1})] · 2Br⁻, n = 12) as template at pH ∼ 6 at room temperature. The products are characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and N₂ adsorption-desorption. The results indicate that anatase TiO₂ exists in both samples and m-SiO₂/TiO₂ has a higher surface area (741.13 m²/g) than m-TiO₂. Moreover, as-synthesized samples show excellent photocatalytic activity for the degradation of methyl red under UV irradiation.     

Solids containing methylhalophosphonium cations [(CH3)n PX+4−n] (n = 1–3 XCl,Br): an investigation using magic-angle spinning NMR spectroscopy

A selection of complexes containing [(CH₃)nPX⁺_4−n] cations (XCl, Br) have been investigated by magic-angle spinning (MAS) ³¹P and ¹¹B NMR spectroscopy. Qualitative information about ionic motion in these systems is derived from the observed linewidths, which are dependent upon the nature of the anions present in the lattices. Isomers of [(CH₃)PCl⁺₃Cl⁻] and [(CH₃)₂PCl⁺₂Cl⁻] are detected, confirming previous Raman spectroscopic observations. The mixed-halogen cations [(CH₃)PCl₂Br⁺], [(CH₃)PClBr⁺₂] and [(CH₃)₂PClBr⁺] are also observed, complexed with both single-halide and polyatomic anions. Differences in NMR linewidths are again noted. These results are compared with Raman studies on the same complexes and contrasted with a similar investigation of the [PCl_nBr⁺_4−n] (O⩽n⩽4) system.     

Synthesis and Surface Properties of Novel Cationic Gemini Surfactants

A series of novel cationic gemini surfactants, p-[C _n H_2n+1N⁺(CH₃)₂CH₂CH(OH)CH₂O]₂C₆H₄·2Cl^? [A(n = 12), B(n = 14) and C(n = 16)], containing a spacer group with two flexible and hydrophilic groups (2-hydroxy-1,3-propylene) on both sides of a rigid and hydrophobic group (1,4-dioxyphenylene) has been synthesized by the reaction of hydroquinone diglycidyl ether with N,N-dimethylalkylamine and N,N-dimethylalkylamine hydrochloride. Their surface-active properties have been investigated by surface tension measurement. The critical micelle concentration (cmc) values of the synthesized cationic gemini surfactants are one order of magnitude lower than those of their corresponding monomeric surfactants (C _n H_2n + 1N⁺(CH₃)₃·Cl^?). Both the cmc and surface tension at the cmc (γ_cmc) of A are lower than those of p-[C₁₂H₂₅N⁺(CH₃)₂CH₂]₂C₆H₄·2Cl^? (D). The novel cationic gemini surfactants A and B also show good foaming properties.     

亚微米级多刺状星形氧化铜的制备

在阳离子gemini表面活性剂[C₁₆H₃₃(CH₃)₂N^＋(CH₂)₄N^＋(CH₃)₂C₁₆H₃₃]•2Br^－ (16-4-16)存在条件下, 以六次甲基四胺为沉淀剂, 利用水热合成法制备了大量多刺状星形亚微米级氧化铜. 用X射线衍射(XRD), X射线光电子能谱(XPS), 扫描电子显微镜(SEM)和透射电子显微镜(TEM)等多种手段对制备产物的表征结果表明, 所得产物是具有单斜结构多刺状星形氧化铜. 考察了表面活性剂浓度、温度以及铜源对产物物相及其形貌的影响.     

FTIR and quantum chemical study of LiBr solvation in acetonitrile solutions

FTIR spectroscopy and quantum chemical calculations at the RTF + MP2/6-311G** level of theory with solvation model density (SMD) corrections were used to study ion solvation and association in LiBr/acetonitrile solutions. The aim of this study was to establish the composition and geometry of the predominant ionic species solvated by acetonitrile molecules and to analyse their spectroscopic signatures. The results obtained make it possible to propose an equilibrium between Li⁺Br⁻(CH₃CN)₃, Li⁺(CH₃CN)₄, and anionic Br⁻(CH₃CN)_n complexes with an undetermined n value and bent coordination of the solvent molecules. The calculated wavenumbers and the geometric parameters of the solvated ionic species were found to be in excellent agreement with the experimental data.     

Solubility in the water-Catamine AB-(alkali metal or ammonium chloride) systems

Solubility in ternary aqueous stratifying systems containing Catamine AB (alkylbenzyldimethylammonium chloride [C _n H_{2n + 1}N⁺(CH₃)₂CH₂C₆H₅] · Cl, a cationic surfactant, where n = 10–18) and LiCl, NaCl, KCl, and NH₄Cl inorganic salts was studied for the first time at 25°C. The boundaries of two-phase liquid equilibrium fields were determined. The studied stratifying systems were proposed for use in the liquid extraction of metal ions.     

ESR Studies on the Micellization Behaviors of a Series of Novel Asymmetric Gemini Surfactants

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Theoretical studies on ferromagnetic behavior of [Cr(C5(CH3)5)2]+[TCNE]− and [Mn(C5(CH3)5)2]+[TCNQ]−

By using broken-symmetry hybrid-DFT (UB3LYP and UB2LYP) calculation, the effective exchange integrals (J values) of [Cr(C₅(CH₃)₅)₂]⁺[TCNE]⁻[Cr(C₅(CH₃)₅)₂]⁺ and [Mn(C₅(CH₃)₅)₂]⁺[TCNQ]⁻[Mn(C₅(CH₃)₅)₂]⁺ were determined theoretically. Those calculated models were reduced to 3-spin-sites models from X-ray crystallographic data of charge transfer 3D crystal. The calculated results showed that effective exchange integrals were positive and the signs of spin densities on the cyclopentadienyl rings were negative. These results supported the so-called McConnell I mechanism for ferromagnetism proposed by Kollmar et al. and our previous calculations. Natural orbital analysis made it clear that the orbital overlap between SOMO on metals and SOMO on TCNE or TCNQ cations was nearly zero. These results indicated that orbital orthogonality was an important key factor for explaining the ferromagnetism of those systems.     

Effect of a Carboxylic Group on the Conformational Properties of Some Gemini Surfactants

Molar volumes of derivatives of N,N-bisdimethyl-1,2-ethanediamine of general formula [C _n H_2n+1OOCCH₂(CH₃)₂N⁺CH₂CH₂N⁺(CH₃)₂CH₂COOC _n H_2n+1]2Cl⁻ (bis-C _n BEC), and betaine ester derivatives of general formula N⁺(CH₃)₃CH₂COOC _n H_2n+1Cl⁻ (C _n BEC), were calculated by means of molecular connectivity indices and an additivity scheme. The COO group contribution in the β-position to the molar volume of bis-C _n BEC was found from experimental data to be significantly lower from that for C _n BEC and was estimated to be 13.5 cm³⋅mol⁻¹. It is suggested that this effect is due to hydrogen bonding between the carboxyl groups via water molecules. Molecular dynamics simulations of bis-C₁₂BEC and 14–2–14 molecules in water were performed and suggest that the upper part of the bis-C₁₂BEC, containing the carboxyl groups, is stiffened by its hydration shell.     

Cationic complexes of trimethylplatinum(IV) with tridentate ligands—I. Preparation and characterization of complexes from a range of thio,seleno, thio-seleno,amino-thio and amino-seleno ligands

The new ionic complexes [PtMe₃{MeE(CH₂)_nE′(CH₂)_nEMe}]⁺X⁻ [n = 3; E = E′ = S : n = 2; E = Se or S; E′ = O, S, Se or SS: X = I, BPh₄ or BF₄] and [PtMe₃(H₂NCH₂CH₂)₂E′]+BF⁻₄ [E′ = O or SS] have been prepared and characterized by molar-conductivity measurements and ¹H NMR spectroscopy. The hitherto unreported ligands [(MeE(CH₂)_n)₂E′] (n = 3; E = E′ = S: n = 2; E = Se; E′ = O or S or Se: n = 2; E = S; E′ = Se] have been characterized by ¹H NMR and ⁷⁷Se NMR (where appropriate), and by mass spectroscopy.     

Observations of magic numbers in gas phase hydrates of alkylammonium ions

Hydration of alkylammonium ions under nonanalytical electrospray ionization conditions has been found to yield cluster ions with more than 20 water molecules associated with the central ion. These cluster ion species are taken to be an approximation of the conditions in liquid water. Many of the alkylammonium cation mass spectra exhibit water cluster numbers that appear to be particularly favorable, i.e., “magic number clusters” (MNC). We have found MNC in hydrates of mono- and tetra-alkyl ammonium ions, NH₃(C _m H_2m+1)⁺(H₂O) _n , m=1–8 and N(C _m H_2m+1) ₄ ⁺ (H₂O) _n , m=2–8. In contrast, NH₂(CH₃) ₂ ⁺ (H₂O) _n , NH(CH₃) ₃ ⁺ (H₂O) _n1 and N(CH₃) ₄ ⁺ (H₂O) _n do not exhibit any MNC. We conjecture that the structures of these magic number clusters correspond to exohedral structures in which the ion is situated on the surface of the water cage in contrast to the widely accepted caged ion structures of H₃O⁺(H₂O) _n and NH ₄ ⁺ (H₂O) _n .     

Morphological Changes of Cationic Gemini Surfactants 14-s-14 (s=4,5,6) in the Presence of Additives

The effect of adding aliphatic alcohols (C₄OH, C₅OH, C₆OH) and corresponding amines (C₄NH₂, C₅NH₂, C₆NH₂) on a series of dicationic gemini surfactants with the general formula C₁₄H₂₉(CH₃)₂N⁺?C(CH₂)_s?CN⁺(CH₃)₂C₁₄H₂₉, 2Br^? (14-s-14; s=4,5,6), in the absence and presence of KNO₃, has been studied by viscosity measurements at 303.15?K. As the chain length of the additive increased, the viscosity increased with increasing additive concentration and the extent of the effect followed the sequence: C₆OH>C₅OH>C₄OH; C₆NH₂>C₅NH₂>C₄NH₂. The simultaneous presence of salt and additives showed an increase in ?? _r values due to a synergistic effect. However, for equal chain lengths in the additives, the effect was greater for the n-alcohols. The tendency for the micelles to grow from spherical to rod-like structures is mainly influenced by the spacer chain length. At 303.15?K, the micellar growth was more pronounced for the shorter spacer, i.e. s being 4, which can be interpreted in terms of the short spacer having a higher tendency for micellar growth. Contrary to the cationic geminis, no effect was observed with a conventional surfactant of equal chain length, TTAB, even in the presence of KNO₃ at the same concentration used for the geminis.     

Synergism in cationic gemini – additive systems

A series of dicationic gemini surfactants with the general formula C₁₆H₃₃(CH₃)₂N⁺?(CH₂)_s?N⁺(CH₃)₂C₁₆H₃₃, 2Br^? (where s?=?4–6), designated as 16-s-16, were synthesised. Their interaction with organic additives: n-alcohols (C₃H₇OH, C₇H₁₅OH, C₈H₁₇OH) and the corresponding amines (C₃H₇NH₂, C₇H₁₅NH₂, C₈H₁₇NH₂) in the absence and presence of KNO₃ at 30°C was studied viscometrically to observe their effect on assembly formation and micellar transition. The simultaneous presence of KNO₃ and organics induced rich aggregates morphologies in the gemini micellar systems by giving high viscosity values. On comparing the behaviour of the gemini surfactant series for a given alkyl chain length of the organic additive, the spacer is found to markedly influence the behaviour; shorter the spacer, earlier the sphere-to-rod transition. In the case of the conventional surfactant, CTAB, the concentration of KNO₃ used with the geminis was insufficient to induce any transition.